Getter for incandescent lamps



Patented Feb. 5, 1935 Ewald Dietz, Bloomfield, N. 1.,

mgh Pennsylvania No Drawing.

This invention relates to incandescent lamp manufacture and more particularlyto an improved method of manufacturing incandescent electric lamps of either the evacuated or gas filled type wherein is employed an improved type of getter material for use in the cleaning up of the residual deleterio gas content of the lamp.

One of the chic ts of the present invention is to improve the life and maintenance of incandescent electric lamps and to facilitate the manufacture of the same.

Another object of this invention is to providea getter material for incandescent electric lamps which is resistant to deterioration at the relatively high temperature conditions that may be applied to the lamp during thesealing in and exhaust operations in the manufacturing'process. Another object of this invention is to provide a stablephosphorus getter composition for use in incandescent electric lamp manufacture.

Another object of'this invention is to more efliciently efiect the clean up and removal of residual atmospheric gases in incandescent electric lamps of the gas filled and evacuated types.

Other objects and advantages will become apparent as the invention is more fully disclosed.

In accordance with the objects of my invention I have found that certain metal phosphide compounds are substantially resistant todeleterious reaction with atmospheric gases at temperatures approximating the, maximum temperatures applied to the lamp during the scaling in and exhaust operations, and that they may be subse- 'quently thermally decomposed into their component elements by heating to more elevated temperatures. a

By incorporating a proportion of metal pho'se phide compounds in an evacuated hermetically sealed container, substantial clean up of residual gases therein may be efiected by thermally de-' composing the metal phosphide'compound. By

incorporating a proportion of a metal phosphide compound in a device containing an atmosphere of relatively inert gases such as nitrogen, argon;

neon, and the like, residual deleterious gases, such as oxygen, moisture and the like may be efiectively removed by the thermal decomposition of the metal phosphide-compound.

' Heretofore in the art it'has been customary to effect theclean up of residual gases in incandescent electric lamps bymeans of phosphorus.

It has been-customary to'introduce the phos-'- phorus intoth'e lamp by admixing a proportion of red phosphorus with an inert material such as cryolite, sodium ferric fluoride or aluminium ouse Lamp Company incandescent lamp lamp it is customary candescent electric'l anip r v H Y that as a result of itheheating ture and'humidityhave' a mark? i 1 the resultant lamp quality by 1 1 7 8 8" manufacturing process.

assignor to westa corporation of Application November 27, 1929, Serial No. 410,257

gases within the lamp'envelope.

The inert constituent is presumed to te epon ized at the same time and in condensingnupon the wall 'of the enclosing glass envelope pro'- vides a film which serves during the life "ofthe '10 device as a medium Ior breaking up;the depositing film of vaporizable material given all by the l filament during operation.

In the manufacture of incandescentelectric lamps it is customary to apply the gettercomposi 1, tion directly to the surface of the lamp filament; or in the case of coil type filamentswithin the interstices, of the turns of the filament. j f

The coated filament is then mounted upon the usual lead-in support wires and thefiare of the stem carrying the mounted filament fusibly united to an enclosing glass envelope in the usual .seal ing in operation. The lamp isfthen exhausted through a tubulature extendingwithin' the envelope through one wall thereof, er'n'ploying chanical exhaust means, and the tubul'ature sealed off when the required or desired degree of vacuum, ,1

During the sealing in andevacuatidnlof the to, apply to the, enclosin V elevated temperatures: ranging from 375 C. to 600 C. depending upon the COIll-i j position of the glass'of the envelope, for the pur pose of eliminating surface adsorbed a fab V sorbed gases upon the glass walls of the envelope". ;3

I have found that the manufacturejoflin" particularly of. the

glass envelope high vacuo type, during the sealing inand exhaustfoperationsi the red phosphoruscomponent of'the getter upon the f filament is suhjected to. bothf,oxidation' d vaporizatiom ,1

This loss in active getter; mater-la M H variations in life and ,of jelectric.i incandescent lamps employing type of'getter and variable conditions of atmospheric tempera creasing the rate rendsetteritnefpimspnqri s 50 content .of the getteridurlng step th a th llma'r 9 stitute for the usual phosphoruscompou i toi'ore employed'a metallicphosphlde" compound, which preferably should besubstantialiy 'Ihave also found inert I have also obtained excellent results be readily decomposed by heat at temperatures component thereof.

Specifically I have found that'copper phosphide compound is the. most serviceable metal phosphide in the practice of my invention, and as a specific embodiment of the application of the same I will disclose the use of this phosphide above about 600 C. to liberate the phosphorus as a clean up agent in incandescent electric lamps of the evacuated type.

It is to be understood that the application of the metal phosphidecompound as a getter will extend equally to the manufacture of incandescent electric lamps of the gas filled type, wherein are employed gas fillings of substantially pure nitrogen, argon or nitrogen-argon mixtures. It is highly essential that this type of getter be employed in gas filled lamps, as residual amounts of moisture and oxygen produce a pronounced effect upon the life and eflic iency of the lamp.

It is essential, however, that the particular metal component of the phosphide be not substantially reactive with the inert gas (nitrogen) filling. I have employed copper phosphide with marked success as a getter in gas ed lamps and with calcium phosphide.

The copper phosphide compound, CllsPz, which may be readily obtained on the market in substantially pure state, is finely pulverized in any convenient manner and is then admixed with the customary cryolite or sodium aluminium ferric fluoride compounds in a proportion which will give from about 3%, ,to about 40% phosphorus when decomposed, the exact proportion being dependent upon the size of the enclosing glass envelope within which it is to be decomposed and the admixture is then applied to the surface of the cut. I prefer to apply the getter by the dry getter" process disclosed in copending application Serial No. 277,106 filed May 11, 1928 by D. S. Gustin which application is assigned to the same assignee as the present invention.

The reason for the preference is that most metal phosphides react with water to liberate phosphine.

organic solvents heretofore. employed inthe dip or "spray-methods of coating filaments contain suflicient amounts 'of water to effect some decomposition of the metal phosphide especially when the getter composition is allowed tostandunused for a period of time. -While this effect will berslight in most cases, it leads to variable results which are not experienced when the dry getter composition of the Gustin method is employed.

The gettered filament is then mounted, sealed within the enclosing glass envelope in the usual manner andthelampexhaustedto ashighadegree as is obtainable by mechanical. exhaust means, applying thereto during the exhaust operation'a temperature of between 375 lie-600" 0.- f0

phosphorus. Metal phosphide compounds.

effect degasification of the enclosing glass envelope.

At the conclusion of the exhaust operation the device is sealed offin the customary manner.

The getter composition upon the surface of the 5 filament is then vaporized by incandescing the filament, the phosphorus component of the metal phosphide compound being evolved and effecting a clean up of the residual gas content of the enclosing. glass envelope. To insure substantial l0 clean up of the residual gases in the device, an oxygenv fiush gas may be employed during the manufacturing process if desired, Phosphorus being highly reactive with oxygen will substantially effect complete removal thereof.

As an example of the benefit obtained by the use of copper phosphide compound as compared to the regular red phosphorus containing getter composition heretofore employed, an average in-'- crease of about 30% hours life may be obtained v with copper phosphide getter over the average Hours life obtainable using red phosphorus alone.

-It is believed that this material increase in life obtained through the use of the copper phosphide compound is due to the fact that the entire clean'up action of the phosphorus component of the phosphide compound is reserved until subsequent to sealing off the lamp'from the exhaust:

pumps.

In the red phosphorus containing getter composition a progressive deterioration of the red phosphorus takes place starting with the first admixing of the phosphorus with the inert cryolite component due to interaction of the phosphorus with atmospheric oxygen and moisture. 36

This deterioration is rapidly accelerated during the sealing in and exhaust operation of the manufacturing process, and the phosphorus content remaining available for subsequent clean up 'of gases is relatively small and certainly variable 40- in amount. This progressive loss of phosphorus in the getter also is materially effected by atmospheric conditions of moisture and temperature as mentioned heretofore.

The advantage obtained through the used 415' metal phosphide in place of the usual phosphorus in the getter is that the phosphide compound is substantially inert, may be readily and easily handled and may be admixed with the cryolite component and kept indefinitely exposed to the air or other atmospheric conditions without deterioration or loss in available phosphorus content. The cryolite-metal phosphide admixture may e suspended in the usual organic suspension medium such as amylacetate containing aldproportion of nitro-celluiose binder without there being any deleterious interaction therebetween.

Through the use of the metal phosphide getter composition a uniformity in life and maintenance in incandescent electric lamps tainable from prior getter compositions is noted indicating that regardless of the variables of exhaust, at pheric humidity, age of getter, the phosphorus content of the metalfphosphide compoundof the getter is substantially preserved dur- 66 mg the.manufacturing processand an effective clean-up of residual gases within the lamp always obtained.

It is to be particularly noted; however, that the advantages of the phosphide getter over the phos- -70 I phorus getter in the manufacture of either gas filled or evacuated lamps is not as pronounced when the best manufacturing conditions are employed in each case. .The advantages, however, will be manifest not heretofore obwhen the manufacturing con- 7 tained irrespective of such variables, as the lamp bulb may be heated to the extreme high temperature of 600 C. during preheat and baking in the scaling in and exhaust steps of the manufacturing process without materially effecting the metal phosphide or without oxidizing or volatilizing the same, and the effects of atmospheric moisture or humidity upon the dry getter is extremely slight owing to the non-absorbing or non-hygroscopic properties of the metal phosphide compound.

' Whereas I have speciflcallyset forth the use -may be similarly employed, the phosof copper phosphide as the phosphorus containing constituent of the getter admixture it; is apparent that other. metal phosphide compounds thereof may extend to gas filled incandescent electric lamps as well aspto the evacuated type.

-It is apparent also that there may be many modifications and combinations 0 specific mainvention and such modiflcationsand departures from the specific embodiment herein disclosed are anticipated as may fall within the scopeof the accompanying claims.

What claimed is:

1. An electric device containing a getter comprised at least in part of CuaPz; I

2. An evacuated device containing a getter comprised at least in part of a thermally decomposable metal phosphide compound, said cointure that is greater than 600 C.

swam 1mm.

and'that the use .terials that may be useful in the practice of this pound in vacuum having a dissociation temperao 

